nerve damage Flashcards
which part of the neurone is able to repair and which isn’t
bodies - cant NO TREATMENT
nerve endings - can LIMITED TREATMENT
describe the role os schwann cells in myelinated and unmyelinated fibres
myelinated schwann cell all the way around 1 per axon individually
unmyelinated wrapping around 5 or so axons
what is endoneurium
microenvironment continuous with subarachnoid space
order of neureums in a nerve
epineureum perineureum endoneurium
name the 2 ways damage to a nerve fibre can occur
- direcly via the axon - axonopathy
- indirectly via the schwann cell - myelinopathy
- indirectly via the endoneurium - neurovascularpathy
define mononeuropathy
mononeuritis multiplex
polyneuropathy
= damage to only one nerve
= affecting two or more isolated nerves in separate areas
= affecting multiple nerves
causes of peripheral neuropathy
idiopathic
inherited
acquired: trauma, infection, disease (diabetes) toxins
What is the grading of nerve injury?
grade 1 - temp and reversible (neuropraxia) - grade 5 complete nn transection (neurotmesis)
what is axonotmesis
loss of axon continuity - graded 2-5
what is Wallerian degeneration
the distal stump undergoes complete
fragmentation, the rate of which is dependent
on
• the type of injury
• the site of injury (PNS»_space; CNS)
• the diameter of the axon
Schwann cells remain as hollow tube
They then dedifferentiate and proliferate
These columns of reactive Schwann cells
(bands of Büngner) become important guides
for sprouting axons during reinnervation.
how do nerve cells regenerate
the proximal axon stump grows along the band of bugner
what does nn cell regrowth depend on
guidance by schwann cells
what happens to schwann cells following axotopy
change their phenotype
- decrease myelin related proteins
- increased adhension related proteins
what happens if the gap in the nn becomes greater than 10 mm during regrowth
neuroma
surgical ways of repairing nn damage
- end to end closure if gap 2cm
- nerve grafting from small cutanous nn
- condutis - synthetic tubes nonneural tissue
describe 4 challenges in the clinical practice of nerve repair
- misgrowth
- slow growth so target organ dies
- ss nn used for grafting to mm nn
- scar tissue formation
name 3 factors which affect the end result of end to end nn surgical repair
age of patient
type of laceration - sharp better
where it is - peripheral repair better
what happenes after nn damage in the CNS?
astrocytes inhibit repair
what is Reactive astrogliosis
astrocytes secreate inhib factors and growth factors to minimise damage (inhib have more effect)
what is a glial scar and what accompanies it
astrocytes make this to isolate damage area. accompanied by CSF filled cyst
when do axons regenerate
newborns, DRP
2 reasons axon regen in the cns fails
surroungings inhib
feeble attempt
why does the cns have growth inhibition
to stop nn growing when theyre not meant to - keep complexity
